Trouble with Context for bpy.ops.transform.translate
Could do it without using the transform.translate operator

import bpy
from mathutils import Vector
# open another file.
bpy.ops.wm.open_mainfile(filepath="/home/batfinger/3DModels/New.blend")

scene = bpy.context.scene
#scene.update()
objects = [o for o in scene.objects]
override = bpy.context.copy()
override["selected_objects"] = objects
override["object"] = objects[0]
bpy.ops.mesh.boundbox_add(override)
bbox = scene.objects.active

for o in objects:
    print(o.name)
    o.location -= bbox.location # origin after translate above

bbox.location -= bbox.location


or run for each scene in the file for scene in bpy.data.scenes

Not a fan of opening new blender file in script as above.  My suggestion would be to use a handler or run a batch command.